Rotatable tundish with multiple outlets

ABSTRACT

A rotatable tundish for the continuous casting of steel is provided with at least two outlet openings through which molten metal may be supplied to the casting mold, said outlet openings being angularly displaced so that while one opening is located in pouring position, the other is located in stand-by position above the level of the molten metal in the tundish.

Elnite States Patent [191 Neumann et al.

ROTATABLE TUNDISH WITH MULTIPLE OUTLETS Inventors: Friedh elm Neumann Adlis wil,

Fritz Willim, FiFmensdofi, both of Switzerland Assignee: Concast AG, Zurich, Switzerland Filed: Sept. 18, 1970 Appl. No.: 73,453

US. Cl. 222/167, 164/336 Int. Cl B67d 5/12 Field of Search 222/181, 146 HE, 222/353, 457, 478, 167, 172, 166, 164, 454, 456; 164/281, 336, 136; 239/393, 394

References Cited UNITED STATES PATENTS Nystrom 164/336 Oct. 16, 1973 1,386,702 11/1918 Gray 222/166 X 1,878,348 9/1932 TeSelle 222/166 3,083,873 I 7/1960 Hirsekorn 222/167 X Primary Examiner-Samuel F Coleman Assistant Examiner-Norman L. Stack, Jr. Attorney-Sandoe, Hopgood & Calimafd'e [57] ABSTRACT A rotatable tundish for the continuous casting of steel is provided with at least two outlet openings through which molten metal may be supplied to the casting mold, said outlet openings being angularly displaced so that while one opening is located in pouring position, the other is located in stand-by position above the level of the molten metal in the tundish.

4 Claims, 4 Drawing Figures PAIENIEDnm \6 ma sum 2 0r 2 FIGZ INVENTORS FRIEDHEL M NEU MANN FRITZ WILLIM ATYORNEYS ROTATABLE TUNDISH WITH MULTIPLE OUTLETS This invention relates to the continuous casting of steel, and pertains to a rotatable drum-shaped tundish having at least two metal pouring outlets which are angularly displaced, so that when one outlet is located in its pouring position above the casting mold, the other outlet is in a stand-by position located above the level of the molten metal in the tundish. The tundish has an inlet opening in the wall of the upper half of the drum, through which molten metal is poured from the ladle into the tundish.

In the continuous casting of steel, a tundish is customarily located between the ladle and the casting mold to act as a molten metal reaservoir and to equalize changes or interruptions in the metal supply from the ladle which sometimes occur during ladle changes or for other reasons. The outlet openings of such tundishes are provided with stopper rods or sliding gages for outlet flow control, with sliding gates becoming increasingly preferred. Tubular nozzles are usually connected to the tundish outlets and preferably extend below the level of the molten metal in the casting mold in order to protect the stream of molten metal between the tundish and the mold against oxidation. They also prevent some slag inclusions from passing into the strand and they improve the metal flow pattern in the liquid core of the strand.

The modern tendency toward increase in ladle size, and the. introduction of so-called continuouscontinuous casting, i.e. in which more than one ladle is poured without interrupting the casting operation, require considerably longer casting times. This exposes the sliding gates and the nozzles to wear for long periods of time, so that the life of these parts tends to limit the casting time. Erosions of nozzles are frequently observed after a relatively short casting time, particularly when casting manganese-alloyed steels, or when the molten metal surface in the mold is covered with flux powder. These erosions sometimes cause parts of the nozzle to break off, thereby permitting undesirable inclusions to penetrate into the lower levels of the liquid core and to be entrapped in the solidifying casting. Sometimes parts of the sliding gate or stopper erode during casting, thus necessitating an interruption in casting.

It is an object of the present invention to provide a rotatable cylindrical or drum-shaped tundish for use in the continuous casting of steel which has at least two metal pouring outlets in its shell which are angularly displaced circumferentially of the shell so that one outlet is located in pouring position above the casting mold, while the other outlet is in a stand-by position located above the molten metal level of the tundish. In this position the stand-by outlet and its associated parts can be repaired or replaced quickly. It is another object of the present invention, to obtain a maximum utilization of the tundish volume, which reduces the cost of the refractory brick lining and also reduces the height of the continuous casting plant.

These and other objects of the invention are obtained by keeping the aperture angle of the tundish equal to or smaller than its rotation angle. The aperture angle is the angle which defines the arc of the opening in the upper part of the cylindrical shell of the tundish, which admits the stream of steel from the ladle, while the rotation angle is the angle through which the tundish is rotated to swing a pouring outlet from its stand-by position into its pouring position above the center of the mold. The angular displacement between the pouring outlets is equal to the rotation angle. As a further feature of the present invention, the ladle can be moved in horizontal directions to place the ladle outlet in different locations above the tundish. Also, the metal stream flowing from the ladle can be deflected from a vertical direction to any desired angle.

It is advantageous to select a rotation angle which is larger than 90, so that steel and slag which is trapped in an outlet passage after the gate or stopper is closed, can be drained into the tundish, after the tundish has been rotated into its stand-by position.

In a preferred form, a rotation angle of about 100 and an aperture angle of about is selected, which permits good utilization of the tundish volume.

As an additional feature of the invention, means may be provided for preheating the nozzle and outlet, while they are in stand-by position, so that they can be used immediately after they have been swung into pouring position.

Embodiments of the present invention are shown in the accompanying drawings in which FIG. 1 is a vertical section of the tundish, the outlet and the mold, with a ladle being shown schematically,

FIG. 2 is a vertical section taken on line IIII of FIG.

FIG. 3 is a vertical section of a tundish having a deflecting trough, and

FIG. 4 shows preheating means for an outlet.

In the embodiment of FIG. 1, a rotatable, drumshaped tundish l is provided with two outlet passages 2, 2. The tundish is lined with refractory brick and conventional sliding gates 3, 3 are mounted on the cylindrical shell 4 for regulating or stopping the flow through the outlet passages 2, 2'. A nozzle 8 having an outlet adapted to extend into the mold and to be submerged in the molten metal in'the mold is attached to the sliding gate 3 to prevent slag inclusions from passing into the liquid core 5 of the strand 6 and also to prevent oxidation of the metal stream between the tundish l and the mold 7.

The outlet passages 2, 2 are angularly displaced on the tundish shell 4 at an angular distance which is equal to the rotation angle 11 heretofore defined. The outlet 2, sliding gate 3 and nozzle 8 are in pouring position above the mold 7, while the outlet passage 2', sliding gate 3 and nozzle 8' are shown in stand-by position. The rotation angle 11 between the pouring position and the stand-by position is in this example about 100, so that the outlet passage 2 is located above the surface of the molten metal reservoir 12. In the stand-by position, the nozzle 8 and the sliding gate 3' can be repaired, or if necessary, replaced in a very short time. Any molten steel and slag which may have been trapped in the outlet passage after the sliding gate was closed, will tend to drain from the outlet cavity into the molten metal reservoir 12 when the tundish is rotated into its stand-by position. solidification of molten steel and slag in the outlet passage 2 can thereby be prevented. A rotation angle which is larger than also permits a relatively high level of the molten metal to be maintained in reservoir 12, which increases the utilization of the volume of the tundish 1.

A stream 13 of molten steel is fed from a ladle into the tundish 1. The ladle may rest on a conventional horizontally movable ladle car (not shown). The steel stream 13 enters the tundish through an opening 16 in the cylindrical tundish shell which extends through an arc on the circumference of the tundish shell which has been referred to as the aperture angle 17. This aperture angle 17 should be equal to or smaller than the rotation angle 11 to insure effective utilization of the tundish volume. In the embodiment shown in FIG. 1 this aperture angle 17 amounts to about 80.

When the tundish is to be rotated through the rotation angle 11, the steel stream 13 flowing from the ladle must be shifted to the location 13 shown in dot-anddash lines. The metal stream 13 can be shifted simultaneously with the rotation of the tundish by horizontal movement of the ladle car. It is also possible to close the ladle gate, then rotate the tundish into its new position, and then to move the ladle into its new position and open its gate after the metal stream location 13' has been reached. Other types of ladles having suitable provision for adjustment to direct the metal stream through the tundish opening 16 can also be used.

An overflow opening 18 may be provided to control the maximum level of molten metal in the reservoir 12. Dot-and-dash lines 16', 18, 13' and 8" designate the location, respectively, of the tundish opening, the overflow opening, the molten steel stream and the nozzle after a rotation through the rotation angle 11 has been completed.

As shown in FIG. 2, the normal level 12 of the molten metal in the tundish is below the longitudinal axis 22 of the tundish by a distance 21. The lower edge of the overflow opening 18 is located at an elevation which is between the normal metal level 12' and the axis 22. Thus, the maximum level can never rise above the axis 22.

The tundish 1 can be raised and lowered, as is known in the prior art, so that the outlet of the nozzles can be submerged below the mold metal level. As shown in FIG. 1, it is possible to rotate the tundish and move the nozzle into the desired submerged position without raising or lowering of the tundish.

The tundish opening 16 which admits the metal stream 13 from the ladle can be designed to be wide enough in direction of the longitudinal axis 22 'to provide easy access for repairs. Each end of the tundish carries a support flange 23 which is rotatably supported in bearings (not shown). As an alternative, the tundish may be provided with concentric rails mounted on the outside of its shell which are guided and supported on rolls. 37 I As a specific example, a tundish of the present invention with an inside diameter of 1,600 mm, an inside length of 2,000 mm and a designed metal level of 700 mm had a designed capacity of 1 1.8 metric tons of molten metal and a maximum capacity of 12.9 metric tons, when the overflow level is 750 mm.

This tundish capacity is sufficient to permit a ladle change in a continuous casting unit having a casting capacity of several tons per minute without having to interrupt the casting process.

It is only necessary to interrupt the metal supply from the tundish into the mold for about 15 seconds while the outlet 2 is rotated from its stand-by position into the pouring position. This short interruption does not require interruption of the continuous casting process.

To increase the utilization of the tundish volume, that part of the tundish cross section which is filled with molten metal could be changed from its semi-circular shape shown in the drawings to an approximately rectangular cross section, with rounded corners.

When a reduction in the height of the casting unit is necessary, then the shape of that part of the tundish which is located below the ladle could be flattened.

FIG. 3 shows a tundish 30 in which a deflecting trough 31 is provided for guiding the molten metal stream 13 into the center of the molten metal reservoir 12. Local erosions of the refractory lining of the tundish 30 are thereby reduced. Furthermore, by the use of such a deflecting trough the aperture angle 17 of the tundish opening 16 may be decreased. This permits the raising of the metal level 12' in the tundish and thereby increases the utilization of the tundish volume. When the tundish is rotated, the steel stream 13 must be shifted to the location 13 and the deflecting trough will be shifted to a corresponding location 31.

FIG. 4 shows the tundish with the nozzle 8' in standby position and provided with means 42, such as gas burners for preheating the nozzles. The preheating means 42 are movable so that they can be used on both sides of the tundish. Instead of gas burners, other preheating means, such as electrical preheaters, could be used.

We claim as our invention:

1. A rotatable tundish for the continuous casting of steel comprising a cylindrical shell having at least two pouring outlets therein, and having an inlet opening through which molten metal may be poured into the tundish, a pouring nozzle connected to each of said outlets, said pouring outlets being angularly displaced circumferentially of said shell by at least and so that when one pouring outlet is in pouring position, the other is in standby position, and said inlet opening having an aperture angle extending circumferentially of said shell over an arc of less than 90.

2. A rotatable tundish according to claim 1 in which said pouring outlets are displaced circumferentially by about and said inlet opening has an aperture angle of about 80.

3. A rotatable tundish according to claim 1 having an nozzle which is in stand-by position. 

1. A rotatable tundish for the continuous casting of steel comprising a cylindrical shell having at least two pouring outlets therein, and having an inlet opening through which molten metal may be poured into the tundish, a pouring nozzle connected to each of said outlets, said pouring outlets being angularly displaced circumferentially of said shell by at least 90* and so that when one pouring outlet is in pouring position, the other is in stand-by position, and said inlet opening having an aperture angle extending circumferentially of said shell over an arc of less than 90*.
 2. A rotatable tundish according to claim 1 in which said pouring outlets are displaced circumferentially by about 100* and said inlet opening has an aperture angle of about 80*.
 3. A rotatable tundish according to claim 1 having an overflow opening with an overflow edge below the longitudinal axis of said cylindrical shell.
 4. A rotatable tundish according to claim 1 including means for preheating the outlet opening and pouring nozzle which is in stand-by position. 